Restraint for marine flotation device

ABSTRACT

A restraint use in a flotation apparatus having components, such as tubular member and couplings, includes a cord having a first end and a second end. Each of the ends is connected to a component. Preferably, the cord is run internally within a tubular member and connects two couplings that are fitted onto opposing ends of the tubular member. The cord has a breaking strength at least sufficient to restrain a coupling when the connection between the coupling and the tubular member is compromised such as when a coupling explosively releases from the tubular member. A method for assembling and operating a floating apparatus includes connecting a coupling to a stationary member, such as a second coupling, using a cord. The method can also include configuring the cord to have a breaking strength that is at least sufficient to restrain a coupling when the connection between the coupling and the tubular member is compromised such as when a coupling explosively releases from the tubular member.

BACKGROUND OF THE INVENTION

[0001] This application is a continuation-in-part of U.S. application Ser. No. 09/270,553 filed Mar. 16, 1999.

FIELD OF THE INVENTION

[0002] This invention relates generally to marine seismic surveying and more particularly to restraining mechanisms used to restrain components of a flotation system for use in marine seismic surveying.

BACKGROUND

[0003] In marine seismic surveying, to obtain geophysical information relating to the substrata located below the sea bottom, seismic sources, generally acoustic transmitters, adapted to produce pressure pulses or shock waves under water, are towed beneath the water surface behind a marine vessel. The shock waves propagate into the substrata beneath the sea where they are refracted and reflected back to the sea. The returning shock waves are detected by seismic sensors (usually hydrophones) and the useful data contained in the signals produced by the sensors is processed to determine the geophysical structure of the substrata.

[0004] Air guns or gas guns are frequently used as acoustic transmitters. Usually, several air guns are placed in spaced relation to each other in a subarray. One or more air gun subarrays are towed behind a marine vessel beneath the sea surface. During operation, all air guns in a subarray are activated simultaneously to produce a desired overall pressure pulse from that subarray. The pulse characteristics, such as the frequency, bubble ratio and amplitude, of the overall pressure pulse produced by an air gun subarray is a function of the characteristics of the pressure pulses produced by the individual air guns and the physical arrangement of the air guns in that air gun subarray.

[0005] In order to repeatedly produce and transmit pressure pulses having known characteristics under water, it is important that the air gun subarray is maintained at a constant depth below the water surface and in a near straight line horizontal position. Air gun subarrays presently in use are generally more than fifty (50) feet long and weigh several hundred pounds.

[0006] To tow such an air gun subarray below the water surface, it is a common practice in the art of seismic surveying to pivotly attach a single or multiple flotation devices (buoys) along the length of the air gun subarray by means of a plurality of links. The flotation device maintains the air gun subarray at or near a constant depth below the water surface when the subarray and the flotation device combination (or the seismic source system) are towed behind a vessel.

[0007] Conventional flotation systems for use in marine seismic acquisition typically consist of sealed metallic containers, sealed members having solid flotation material in separate compartments, or sealed members that communicate with one another using a series of valves and a regulated air supply. Flotation systems consisting of sealed metal containers frequently suffer from premature failure in operation because of water infiltration of the inflexible metal container. Flotation systems consisting of sealed members having solid flotation materials in separate compartments are complex and difficult to monitor in operation. Flotation systems consisting of sealed members that communicate with one another and include a regulated air supply are complex and require a regulated power supply, valving, and a controller.

[0008] Furthermore, typical flotation systems do not include devices that ameliorate the effects of a failure of a connection between components of a prior art flotation system. The connection between components of a typical prior art flotation system may be compromised during both the assembly and subsequent use of the system. For example, a coupling attached to a tubular member may explosively release from the tubular member if exposed to excessive gas pressure during the inflation stage of the assembly of the flotation system. By “explosively release,” it is meant that the mechanical connections, such as band clamps, holding a coupling to a tubular member are overcome by the high pressure air introduced into the flotation system. The high pressure air causes the coupling to be thrust out of the tubular member. Such a coupling can be, effectively, a high speed projectile that poses a threat to personnel and equipment. Some systems rely on regulator devices, check valves or pressure relief valves to prevent excessive pressure. However, these mechanical devises are relatively complex and apt to fail when subjected to the corrosive environment of the sea.

[0009] The connections associated with conventional flotation devices may also be compromised during use of these devices. As described earlier, flotation devices are towed at or immediately below the ocean surface during seismic survey operations. The towing action coupled with the harsh marine environment may loosen one or more flotation device connections. The loosening of the connections may, for example, cause slippage between the coupling and adjacent tubular member. This slippage may lead to a loss of buoyancy, increased towing drag and instability and create added difficulties during retrieval of equipment.

[0010] The present invention is directed to overcoming one or more of the limitations of the above-described flotation systems used for marine seismic energy source.

SUMMARY OF THE INVENTION

[0011] The present invention includes a restraint for use in a flotation apparatus having components, such as tubular member and couplings, that are joined with connections that may become compromised during assembly or use. In an advantageous application, a preferred restraint includes a cord having a first end and a second end. Each of the ends is connected to a coupling with an engaging member that can selectively engage a mount provided on the couplings. The cord is run internally within a tubular member and the two couplings are fitted onto opposing ends of the tubular member. The cord has a breaking strength at least sufficient to restrain a coupling when the connection between the coupling and the tubular member is compromised. Preferably, the breaking strength is at least sufficient to restrain a coupling that explosively releases from the tubular member. In other applications, the cord may be used to restrain other flotation apparatus components.

[0012] The present invention also provides a method for assembling and operating a floating apparatus that includes connecting a coupling and a stationary member using a cord. This stationary member may be a second coupling. The method can also include configuring the cord to have a breaking strength that is at least sufficient to restrain a coupling when the connection between the coupling and the tubular member is compromised such as when a coupling explosively releases from the tubular member.

[0013] It should be understood that examples of the more important features of the invention have been summarized rather broadly in order that detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A better understanding of the present invention can be obtained when the following detailed description of exemplary embodiments are considered in conjunction with the following drawings, in which:

[0015]FIG. 1 is a schematic illustration of an embodiment of a marine seismic acquisition system;

[0016]FIG. 2 is an illustration of an embodiment of a flotation device for marine seismic energy sources for use in the marine seismic acquisition system of FIG. 1;

[0017]FIG. 3 is a cross-sectional illustration and view of the flotation device of FIG. 2;

[0018]FIG. 4 is an illustration of an embodiment of the head float of the flotation device of FIG. 2;

[0019]FIG. 5 is an illustration of another embodiment of the head float of FIG. 4;

[0020]FIG. 6 is another cross-sectional illustration and view of the flotation device of FIG. 2;

[0021]FIG. 7 is another cross-sectional illustration and view of the flotation device of FIG. 2;

[0022]FIG. 8 is an illustration of an embodiment of the coupling of the flotation device of FIG. 2;

[0023]FIG. 9 is an illustration of another embodiment of the coupling of FIG. 8;

[0024]FIG. 10 is a fragmentary cross-sectional view of a preferred embodiment of the coupling of the flotation device of FIG. 2;

[0025]FIG. 11 is a cross-sectional illustration and view of the coupling of FIG. 10;

[0026]FIG. 12 is another cross-sectional illustration and view of the flotation device of FIG. 2;

[0027]FIG. 13 is an illustration of an embodiment of the tail member of the flotation device of FIG. 2;

[0028]FIG. 14 is an illustration of another embodiment of the tail member of FIG. 13; and

[0029]FIG. 15A is an illustration of an embodiment of a preferred restraint, shown in phantom, used in conjunction with the flotation device of FIG. 2.

[0030]FIG. 15B is an illustration of a side-view of embodiment of a preferred restraint used in conjunction with the flotation device of FIG. 2, the flotation device being shown in partial cut-away.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

[0031] In the description which follows, like parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawing figures are not necessarily drawn to scale and certain figures may be shown in exaggerated or generalized form in the interest of clarity and conciseness.

[0032] A flotation device for marine seismic energy sources is provided. The flotation device preferably includes a head float, a plurality of tubular members, couplings, and a tail member. Each of the tubular members in combination with a pair of the couplings provide a sealed flotation member.

[0033] Furthermore, each of the couplings includes an air valve for injecting a buoyant fluid into the interior of the tubular members. In this manner, the flotation device provides a compact and modular flotation device that preferably includes a plurality of buoyant members. Furthermore, in this manner, the length of the flotation device may be easily adjusted in operation by adding or subtracting tubular members and couplings. While illustrated in an exemplary embodiment as a flotation device for marine seismic energy sources, the present flotation device will have wide application to any number of applications that would be enhanced by the application of a modular flotation device.

[0034] Referring initially to FIG. 1, a marine seismic acquisition system 100 includes a controller 105, one or more marine seismic sensors 110, and a marine seismic energy source 115. The marine seismic acquisition system 100 preferably monitors and controls the collection of seismic data for a subterranean formation.

[0035] The controller 105 controls the operation of the marine seismic acquisition system 100. The controller 105 may comprise any number of conventional commercially available controllers for marine seismic acquisition such as, for example, a WG-24 or Syntrac. In a preferred embodiment, the controller 105 comprises any one of the commercially available controllers from Input/Output, Inc. in Stafford, Tex.

[0036] The marine seismic sensors 110 sense seismic energy and generate electrical signals representative of the measured seismic energy. The marine seismic sensors 110 are operably coupled to the controller 105. The marine seismic sensors 110 may comprise any number of conventional commercially available marine seismic sensors such as, for example, WG-24 or Syntrac. In a preferred embodiment, the marine seismic sensors 110 comprise any one of the commercially available marine seismic sensors from Input/Output, Inc. in Stafford, Tex.

[0037] The marine seismic energy source 115 is operably coupled to the controller 105. The marine seismic energy source 115 generates seismic energy in a well known manner under the control of the controller 105.

[0038] Referring to FIGS. 2-13, in a preferred embodiment, the marine seismic energy source 115 includes a flotation device 200 and one or more energy sources 205. The flotation device 200 is preferably adapted to float on the surface 210 of a body of water 215. The flotation device 200 further is preferably adapted to support one or more energy sources 205 positioned below the surface 210 of the body of water 215.

[0039] As illustrated in FIG. 2, in a preferred embodiment, the flotation device 200 includes a head float 220, a first tubular member 225 a, one or more intermediate tubular members 225 b, a last tubular member 225 c, couplings 230, clamps 235, and a tail member 240. In the general application of the flotation device 200, the device 200 includes a head float 220, n tubular members 225, n-1 couplings 230, and a tail member 240.

[0040] The head float 220 is coupled to the first tubular member 225 a. The head float 220 is preferably adapted to float on the surface 210 of the body of water 215. As illustrated in FIGS. 3 and 4, the head float 220 preferably includes an elongate body 305 having a hollow interior 310. In this manner, the interior 310 of the head float 220 may be filled with a buoyant fluid such as, for example, air. In an alternative preferred embodiment, at least a portion of the interior 310 of the head float 220 comprises a solid flotation material such as, for example, Styrofoam. In this manner, the head float 220 is prevented from sinking below the surface 210 of the body of water 215 in the event of an air leak.

[0041] In a preferred embodiment, the body 305 of the head float 220 further includes an open end 315 adapted to fit within one end of the first tubular member 225 a. In this manner, the interior of the head float 220 may be fluidicly coupled to the interior of the first tubular member 225 a. In a preferred embodiment, the open end 315 of the body 305 of the head float 220 is removably coupled to the first tubular member 225 a using a clamp 235. In a preferred embodiment, the clamp 235 provides sufficient force to ensure an air and fluid tight seal between the outer surface of the open end 315 of body 305 of the head float 220 and the inner surface of the first tubular member 225 a.

[0042] As illustrated in FIG. 5, in a preferred embodiment, the exterior surface of the open end 315 of the body 305 of the head float 220 includes one or more ribbed surfaces 335 in order to enhance the connection between the open end 315 of the body 305 of the head float 220 and the first tubular member 225 a. In a preferred embodiment, the exterior surface of the open end 315 of the body 305 of the head float 220 includes one or more flexible sealing members in order to optimally provide a fluid and air tight seal between the open end 315 of the body 305 of the head float 220 and the first tubular member 225 a.

[0043] The body 305 of the head float 220 may be fabricated from any number of conventional commercially available materials such as, for example, polyethylene, PVC or fiberglass. In a preferred embodiment, the body 305 of the head float 220 is fabricated from polyethylene in order to optimally provide impact resistance.

[0044] The clamp 235 may comprise any number of conventional commercially available clamping devices such as, for example, hose clamps, bands or straps. In a preferred embodiment, the clamp 235 comprises multiple bands available from Band-It in order to optimally provide air tightness. In a preferred embodiment, the clamp 235 provides a contact pressure between the interior surface of the first tubular member 225 a and the exterior surface of the head float 220 to provide a fluid and air tight seal between the first tubular member 225 a 'and the head float 220.

[0045] In a preferred embodiment, a harness 325 is coupled to the outer surface of the body 305 of the head flow 220. In a preferred embodiment, the harness 325 is coupled to an anchoring device using a flexible cable 330. In this manner, the flotation device 200 may be positioned is a substantially stationary location on the surface 210 of the body of water 215. The harness 325 may comprise and number of conventional commercially available harnesses such as, for example, rope, chain or straps. In a preferred embodiment, the harness 325 comprises a formed metal strap in order to optimally provide a secure attachment location.

[0046] As illustrated in FIG. 2, the first tubular member 225 a is preferably coupled to the head float 220 and to one of the couplings 230. The intermediate tubular members 225 b are preferably each coupled to a pair of the couplings 230. The last tubular member 225 c is preferably coupled to one of the couplings 230 and to the tail member 240. The tubular members, 225 a, 225 b and 225 c, preferably comprise hollow elongate tubular bodies 605 having interior chambers 610. The tubular members 225 a, 225 b and 225 c may be fabricated from any number of conventional commercially available materials such as, for example, urethane, synthetic rubber or polyethylene. In a preferred embodiment, the tubular members 225 a, 225 b and 225 care fabricated from reinforced synthetic rubber available from Unaflex in order to optimally provide flexibility and durability. As illustrated in FIGS. 6, 7 and 8, each of the couplings 230 preferably comprise a substantially tubular body 805 including a partition 810 that separates the interior of the tubular body 805 into two interior chambers 815 a and 815 b. In a preferred embodiment, one of the interior chambers is fluidicly coupled to the interior of one of the tubular members 225 and the other one of the interior chambers is fluidicly coupled to the interior of another one of the tubular members 225. The couplings 230 may be fabricated from any number of conventional commercially available materials such as, for example, aluminum or plastic. In a preferred embodiment, the couplings 230 are fabricated from aluminum in order to optimally provide structural integrity, light weight, and corrosion resistance.

[0047] The couplings 230 further preferably include at least one valve 820 that permits a corresponding one of the interior chambers, 815 a or 815 b, to be injected with a buoyant fluid. The valve 820 may comprise any number of conventional commercially available valves such as, for example, ball, tank, or tire valves. In a preferred embodiment, the valve 820 comprises a large bore tire valve available from Haltec, Inc. in order to optimally provide rapid filling and automatic sealing. In an alternative embodiment, one or more of the couplings 230 include a separate valve 820 for each of the interior chambers, 815 a and 815 b. In this manned, both interior chambers, 815 a and 815 b, may be injected with a buoyant fluid. In a preferred embodiment, the buoyant fluid comprises air.

[0048] As illustrated in FIG. 9, in a particularly preferred embodiment, the couplings 230 include ribbed outer surfaces 905 at each end of the tubular body 805 in order to facilitate the coupling of the couplings 230 to the tubular members 225 a, 225 b and 225 c. In a preferred embodiment, the outer surface of the couplings 230 include flexible sealing members at each end of the tubular body 805 in order to optimally provide a fluid and air tight seal between the couplings 230 and the tubular members 225 a, 225 b and 225 c.

[0049] As illustrated in FIGS. 6, 7 and 8, the first tubular member 225 a is coupled at one end to one of the couplings 230. In a preferred embodiment, the first tubular member 225 a is coupled to one of the couplings 230 by inserting one end of the tubular body 805 of the coupling 230 into the interior chamber 610 of the tubular body 605 of the first tubular member 225 a. In this manner, the interior chamber 610 of the first tubular member 225 a is fluidicly coupled to the interior chamber 815 a of the coupling 230.

[0050] Furthermore, in this manner the interior chamber 310 of the head float 220 is also preferably fluidicly coupled to the interior chamber 815 a of the coupling 230. In this manner, the interior chambers, 310 and 610, of the head float 220 and first tubular member 225 a may be injected with a buoyant fluidic material using the valve 820 of the coupling 230.

[0051] As illustrated in FIG. 2, the intermediate tubular members 225 b are coupled at both ends to one of the couplings 230. As illustrated in FIGS. 2, 6, 7 and 8, in a preferred embodiment, the intermediate tubular members 225 b are coupled to the couplings 230 by inserting one end of the tubular body 805 of one of the couplings 230 into one end of the interior chamber 610 of the tubular body 605 of the intermediate tubular member 225 a, and by inserting one end of the tubular body 805 of another one of the couplings 230 into the other end of the interior chamber 610 of the tubular body 605 of the intermediate tubular member 225 a. In this manner, the interior chambers 610 of the intermediate tubular members 225 a are fluidicly coupled to the interior chambers, 815 a and 815 b, of the pair of couplings 230. Furthermore, in this manner, the interior chambers, 815 a and 815 b, of the pair of couplings 230 and interior chamber 610 of the intermediate tubular members 225 b may be injected with a buoyant fluidic material by using the valve 820 of one of the couplings 230. In an alternative embodiment, the couplings 230 include a separate valve for each of the interior chambers, 815 a and 815 b.

[0052] In a preferred embodiment, clamps 235 are used to compress the interior surface of the intermediate tubular members 225 b onto the exterior surfaces of the ends of the couplings 230. In a preferred embodiment, the clamps 235 provide a contact pressure between the intermediate tubular members 225 b and the couplings 230 that ranges from about 5 to 10 psi in order to optimally provide a fluid and air tight seal between the intermediate tubular members 225 b and the couplings 230.

[0053] In a preferred embodiment, a harness 615 is coupled to the exterior surface of each of the couplings 230 for supporting a corresponding one of the marine seismic energy source 205. In a preferred embodiment, a flexible cable 620 is used to couple the harness 615 to the marine seismic energy source 205.

[0054] As illustrated in FIGS. 2, 12 and 13, the last tubular member 225 c is coupled to one of the couplings 230 and to the tail member 240. The connection of one end of the last tubular member 225 c to one end of one of the couplings 230 is preferably provided substantially as described above with reference to the connection of the intermediate tubular members 225 b to the couplings 230.

[0055] The tail member 240 preferably includes a tubular elongate body 1305 having an end wall 1310, a valve 1315, and an interior chamber 1320. The tubular body 1305 of the tail member 240 may be fabricated from any number of conventional commercially available materials such as, for example, steel, aluminum or plastic. In a preferred embodiment, the tubular body 1305 of the tail member 240 is fabricated from aluminum.

[0056] The last tubular member 225 c is preferably coupled to the tail member 240 by inserting a portion of the open end of the tail member 240 into one end of the last tubular member 225 c. In this manner, the inner chamber 610 of the last tubular member 225 c is fluidicly coupled to the interior chamber 1320 of the tail member 240. Furthermore, in this manner, the interior chamber 815 b of the coupling 230, that is coupled to the other end of the last tubular member 225 c, is fluidicly coupled to the interior chamber 610 of the last tubular member 225 c and the interior chamber 1320 of the tail member 240. In a preferred embodiment, the interior chamber 815 b of the coupling 230, that is coupled to the other end of the last tubular member 225 c, the interior chamber 610 of the last tubular member 225 c, and the interior chamber 1320 of the tail member 240 are injected with a buoyant fluid using the valve 1315. The valve 1315 may comprise any number of conventional commercially available valves such as, for example, ball, tank or tire valves. In a preferred embodiment, the valve 1315 comprises a large bore tire valve available from Haltec, Inc. in order to optimally provide rapid filling and automatic sealing. In an alternative embodiment, the last tubular member 225 c is coupled at both ends to one of the couplings 230. In this manner, additional tubular members 225 are easily added to the flotation device 200.

[0057] In a preferred embodiment, a clamp 235 is used to compress the interior surface of one end of the last tubular member 225 c onto the exterior surface of the open end of the tail member 240. In a preferred embodiment, the clamp 235 provides a contact pressure between the interior surface of one end of the last tubular member 225 c and the exterior surface of the open end of the tail member 240 that ranges from about 5 to 10 psi in order to optimally provide a fluid and air tight seal between the last tubular member 225 c and the tail member 240. In a preferred embodiment, as illustrated in FIG. 14, the exterior surface of the open end of the tail member 240 includes one or more ribbed surfaces 1405 to facilitate the connection between the last tubular member 225 c and the open end of the tail member 240. In a preferred embodiment, the exterior surface of the open end of the tail member 240 includes one or more flexible sealing members in order to optimally provide a fluid and air tight seal between the last tubular member 225 c and the open end of the tail member 240.

[0058] The energy sources 205 are coupled to the harnesses 615 and 620. The energy sources 205 are preferably positioned below the surface 210 of the body of water 215. The energy sources 205 may comprise any number of conventional commercially available marine seismic energy sources such as, for example, air guns, gas exploder or vibrators. In a preferred embodiment, the energy sources 205 comprise air guns available from Input/Output, Inc. in Stafford, Tex.

[0059] Thus, the flotation device 200 preferably includes a plurality of buoyant members that include: (1) the combination of the head float 220, first tubular member 225 a, and a coupling 230; (2) the combination of at least one intermediate tubular member 225 b and a pair of couplings 230; and (3) the last tubular member 225 c and a coupling 230 and the tail member 240. Each of these buoyant members are preferably injected with a buoyant fluid such as, for example, air using the valves positioned in the walls of the couplings 230 and the tail member 240. The design and construction of the flotation device 200 permits the number and length of the buoyant members to be easily adjusted in operation. In the general application of the flotation device 200, the device 200 includes: (1) a head float; (2) n tubular members; (3) n-i couplings; and (4) a tail member. In an alternative embodiment, at least a portion of the interior of the head float 220 comprises a solid flotation material such as, for example, Styrofoam.

[0060] In a preferred embodiment, as illustrated in FIGS. 10 and 11, the flotation device 200 includes couplings 1005 and tubular members 1010.

[0061] The couplings 1005 include an elongate tubular body 1015 having a partition 1020, a first inner chamber 1025 a, a second inner chamber 1025 b, an opening 1030, a valve 1035, ribbed surfaces 1040, and a valve mounting member 1045. The partition 1020 divides the interior of the tubular body 1015 into the first and second inner chambers, 1025 a and 1025 b. The couplings 1005 may be fabricated from any number of conventional commercially available materials such as, for example, aluminum or plastic. In a preferred embodiment, the couplings 1005 are fabricated from aluminum in order to optimally provide lightweight and high strength.

[0062] The opening 1030 in the side wall of the tubular body 1015 permits the valve mounting member 1045 to be mounted within the interior of the tubular body 1015. The valve 1035 permits the injection of a buoyant fluid into the inner chamber 1025 a. The valve 1035 may comprise any number of conventional commercially available valves such as, for example, ball, tank, or tire valves. In a preferred embodiment, the valve 1035 comprises a large bore tire valve available from Haltec, Inc. in order to optimally provide rapid filling and automatic sealing.

[0063] The valve mounting member 1045 preferably comprises a tubular member having an end wall including a through hole for mounting the valve 1035. The open end of the valve mounting member 1045 preferably includes an outer groove that engages with the edges of the opening 1030 in the tubular body 1015 of the coupling 1005. In this manner, the valve mounting member 1045 is mounted within the interior of the tubular body 1015 of the coupling 1005. This permits the valve 1035 to be recessed below the outer surface of the tubular body 1015 of the coupling 1005.

[0064] The tubular members 1010 preferably comprise elongate tubular elements having an opening 1050 that corresponds to and matches up with the opening 1030 in the side wall of the tubular body 1015 of the couplings 1005. In this manner, the recessed valve 1025 may be accessed by an operator. The tubular members 1010 may be fabricated from any number of conventional commercially available materials such as, for example, urethane, synthetic rubber, polyethylene. In a preferred embodiment, the tubular members 1010 are fabricated from reinforced synthetic rubber available from Unaflex in order to optimally provide flexibility and durability.

[0065] In a preferred embodiment, the couplings 1005 include a separate valve for each of the inner chambers, 1025 a and 1025 b. In this manner, the tubular members 1010 coupled to each of the inner chambers, 1025 a and 1025 b, may be injected with a buoyant fluid using the same coupling 1005.

[0066] Referring now to FIG. 15A, a restraint 1500 (shown in phantom) made in accordance with the present invention minimizes the risk of injury to personnel and damage to equipment that may result if a connection between components of a flotation system 1502 is compromised. An exemplary flotation system 1502 can include components such as tubular members 1504, couplings 1506, a head float 1508 and a tail end 1510.

[0067] Referring now to FIG. 15B, the restraint 1500 restrains or captures a component making up the flotation system 1502 (e.g., tubular members, couplings, a head float or a tail end) by tethering that component to an adjacent component. Thus, the adjacent component acts as stationary member for the tethered component. By “restrain” or “capture,” it is meant that the movement of a coupling 1506, or other component, is limited to a range that does not substantially impair the structural integrity of the flotation system 1502 or pose a threat to personnel and equipment. While the restraint 1500 may be advantageously used to restrain nearly any component of the flotation system 1502, for simplicity, the present discussion will be directed to a preferred restraint 1500 adapted to restrain the couplings 1506 associated with the flotation system 1502. A preferred restraint 1500 so adapted is generally disposed within the tubular members 1504 and includes a lanyard 1520 and mounts 1530.

[0068] A lanyard 1520 physically connects a coupling 1506 to a stationary member or component, such as an adjacent coupling. A preferred lanyard 1520 includes a cord 1522 having ends 1524 and engaging members 1526 provided thereon. The cord 1522 may be a cable, chain, belt, or other suitable compliant member. Preferably, the cord 1522 is configured to restrain a coupling when the connection between the coupling and the tubular member is compromised. It is also preferable that the breaking strength of the cord 1522 be sufficient to restrain a coupling 1506 that explosively releases from a tubular member 1504. By “breaking strength,” it is meant the amount of tension, torsion or other type of loading the cord 1522 can withstand before the cord 1522 become ineffective to restrain the coupling 1506. The acceptable breaking strength depends on factors such as material properties, the size of the coupling 1506, maximum gas pressure to which the coupling 1506 may be subjected, and any applicable safety factors. Polypropylene is a preferred material used in the manufacture of the cord 1522 because this material is relatively inexpensive, lightweight and easy to splice and exhibits adequate breaking strength for most applications. However, a wide variety of materials can be implemented without detracting from the spirit of the invention, including but not limited to steel wire, rope, Kevlar, nylon, polyester, natural fibers and synthetic fibers.

[0069] The engaging members 1526 of the lanyard 1520 join the cord 1522 to the mounts 1530. The engaging members 1526 are located on each end 1524 of the lanyard 1520. A preferred engaging member 1526 includes an eye splice or similar loop-like configuration formed on each cord end 1524. Alternate engaging members include an eye formed using saddle clamps, a potted termination, a hook or any other similar device that can secure the cord 1522 to the mount 1530. The engaging member 1526 may optionally be provided with a mechanism (not shown) to adjust the length of the cord 1522 to facilitate assembly of the flotation device 1502.

[0070] Mounts 1530 provide an attachment location on the couplings 1506 for the lanyard engaging members 1526. A preferred mount 1530 includes a lug 1532 and a shackle 1534. The lug 1532 is a plate member having a hole 1533 and that is welded or otherwise fixed onto the coupling 1506. The shackle 1534 is adapted to mate with the lanyard engaging member 1526. The shackle 1534 is disposed within the lug hole 1533 and is formed to receive the engaging member 1526. The shackle 1534 may include a latch (not shown) that opens to receive, for example, an eye splice, and closes to capture the eye splice within the shackle 1534, thereby providing selective engagement between the lanyard 1520 and the mount 1530.

[0071] It should be understood that the above-described engaging members 1526 and the mount 1530 are merely exemplary of the many mechanical arrangements available to provide selective engagement between the lanyard 1520 and adjacent couplings 1506. One of ordinary skill in the art will appreciate that alternate mechanical arrangements, e.g., threaded fasteners, 0-ring shackles, safety hooks, or quick-disconnects, can also function as the attachment mechanism. Furthermore, the engaging members 1526 and the mounts 1530 should not be understood to necessarily be distinct from the coupling 1506 or any other component. For example, the mounts 1530 may be formed integrally with the coupling 1506. Indeed, the coupling 1506 may already incorporate a feature such as a ledge, orifice, or protrusion that can be used as an attachment location in lieu of a separate mount 1530. Thus, the present invention is not limited to any of the described embodiments of the engaging members 1526 or the mounts 1530.

[0072] From the above, it can be seen that the present invention is amenable to numerous variations. For example, the lanyard 1520 may be run on the outside of the flotation device 1502 rather than internally through the tubular members 1504. Also, a single cord 1522 may link multiple couplings 1506. Furthermore, the cord 1522 need not link only immediately adjacent couplings 1506. Rather, the cord 1522 may, for example, attach to a first coupling, pass through a medial coupling and attach to a second coupling. Moreover, as noted earlier, the restraint may be used to restrain any component of the flotation device 1502. The configuration of the restraint 1500 is, thus, generally dictated by expected difficulties that may arise during assembly and use of the flotation device 1502. The operation of the restraint 1500 during such assembly and use is discussed herein below.

[0073] The following description of the assembly and use of the preferred restraint presumes familiarity with the above-described elements and, therefore, dispenses with the numerals corresponding to these elements. One stage in the assembly of a flotation device may require that a first and second coupling be fitted onto a tubular member. Before this stage, one engaging member of a lanyard is attached to a mount that is fixed on the first coupling. After the lanyard cord is run through the tubular member, the first coupling is fastened to the tubular member. The other engaging member of the lanyard is then attached to a mount on the second coupling. The adjusting mechanism, if present, may be used lengthen or shorten the cord. Thereafter, the second coupling is fitted onto the tubular member. This process is repeated for the remaining tubular members and associated couplings. The couplings at the outer ends of the flotation device may be connected to a tail member or a head float. Upon assembly, high-pressure gas may be used to inflate the tubular members of the flotation. During inflation, the first coupling may explosively release from a tubular member. The connection between first coupling and the tubular member may suffer such a failure due to defects in the connection or excessive gas pressure in the tubular member. In either case, the cord, which is attached to the generally stationary first coupling, permits the first coupling to travel a predetermined distance from the second coupling. Thus, the second coupling acts as a stationary anchor for the first coupling, thereby preventing the first coupling from becoming an untethered projectile that poses a hazard to personnel and equipment.

[0074] During use of the flotation device in a surveying operation, tubular members are towed by a vessel through water. Destabilizing forces such as the tension induced by the towing and waves striking tubular members may loosen or otherwise compromise the connections between couplings and tubular members. The preferred restraint, in this situation, performs two related functions. First, the preferred restraint can supplement the connections between the couplings and tubular members, or other components, such that they can withstand a greater amount of destabilizing force. Second, if any of these connections were to fail, then the preferred restraint will hold the fragmented tubular members together so that flotation device may be easily retrieved.

[0075] A flotation device for a marine seismic energy source has been described that includes a head float, n tubular members coupled to the head float, n-I couplings coupled to the tubular members for sealing an end portion of the tubular members, each coupling including an air valve, and a tail member coupled to an end portion of one of the tubular members for sealing the end portion of the one tubular member. In a preferred embodiment, the tubular members comprise flexible tubular elements. In a preferred embodiment, the tubular members are fabricated from materials selected from the group consisting of urethane, synthetic rubber, and polyethylene. In a preferred embodiment, the couplings comprise: a tubular member having an interior divided by a partition into two sections, and an air valve coupled to one of the two interior sections. In a preferred embodiment, the tail member comprises: a tubular member having an interior section, and an air valve coupled to the interior section.

[0076] A marine seismic energy source has also been described that includes a flotation device and one or more marine seismic energy sources coupled to the flotation device. The flotation device includes: a head float, n tubular members coupled to the head float, n-1 couplings coupled to the tubular members for sealing an end portion of the tubular members, each coupling including an air valve, and a tail member coupled to an end portion of one of the tubular members for sealing the end portion of the one tubular member. In a preferred embodiment, the tubular members comprise flexible tubular elements. In a preferred embodiment, the tubular members are fabricated from materials selected from the group consisting of urethane, synthetic rubber and polyethylene. In a preferred embodiment, the couplings comprise: a tubular member having an interior divided by a partition into two sections, and an air valve coupled to one of the two interior sections.

[0077] In a preferred embodiment, the tail member comprises: a tubular member having an interior section, and an air valve coupled to the interior section. A marine seismic acquisition system has also been described that includes a controller for controlling the operation of the marine seismic acquisition system, one or more marine seismic sensors for monitoring seismic energy coupled to the controller, and a marine seismic energy source for generating seismic energy coupled to the controller. The marine seismic energy source includes a flotation device and one or more marine seismic energy sources coupled to the flotation device. The flotation device includes a head float, n tubular members coupled to the head float, n-i couplings coupled to the tubular members for sealing an end portion of the tubular members, each coupling including an air valve; and a tail member coupled to an end portion of one of the tubular members for sealing the end portion of the one tubular member. In a preferred embodiment, the tubular members comprise flexible tubular elements. In a preferred embodiment, the tubular members are fabricated from materials selected from the group consisting of urethane, synthetic rubber and polyethylene. In a preferred embodiment, the couplings comprise: a tubular member having an interior divided by a partition into two sections, and an air valve coupled to one of the two interior sections.

[0078] In a preferred embodiment, the tail member comprises: a tubular member having an interior section, an air valve coupled to the interior section. A flotation member has also been described that includes a tubular member having an interior chamber with first and second ends, a first sealing member for sealing the first end of the interior chamber of the tubular member, and a second sealing member for sealing the second end of the interior chamber of the tubular member. At least one of the sealing members includes a valve for injecting a buoyant fluid into the interior chamber of the tubular member.

[0079] A sealing member for sealing a hollow tubular member has also been described that includes a hollow tubular housing having a first end and a second end, a partition positioned within the hollow tubular housing for dividing the interior of the hollow tubular housing into a first interior portion and a second interior portion, and a valve coupled to the hollow tubular housing. A method of operating a marine seismic energy system has also been described that includes providing a plurality of separate flexible buoyant members, coupling the flexible buoyant members, injecting a buoyant fluid into the flexible buoyant members, and supporting at least one marine seismic source beneath the surface of a body of water using one or more of the buoyant members.

[0080] A method of floating one or more elements below the surface of a body of water has also been described that includes providing a tubular flotation member, sealing the end of the tubular flotation member, injecting a buoyant fluid into the tubular flotation member adjacent to one of the ends of the tubular flotation member, and supporting one or more elements below the surface of a body of water using the tubular flotation member. A method of joining flotation devices has also been described that includes providing a flexible hollow coupling including a valve for injecting a buoyant fluid into the flotation devices.

[0081] Although illustrative embodiments of the invention have been shown and described, a wide range of modification, changes and substitution is contemplated in the foregoing disclosure. In some instances, some features of the present invention may be employed without a corresponding use of the other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention. 

What is claimed is:
 1. A device for a flotation apparatus having a tubular member with opposing ends and a coupling disposed on each opposing end, the device comprising: a cord having a first end and a second end, each of said first and second ends being connected to a coupling.
 2. The device of claim 1 wherein said cord is disposed at least partially within the tubular member.
 3. The device of claim 1 further comprising an engaging member provided on each of said cord first and second ends, said engaging members being selectively engagable with the couplings.
 4. The device of claim 1 wherein said cord is configured to restrain at least one of the couplings when the connection between the restrained coupling and the tubular member is compromised.
 5. The device of claim 1 wherein said cord is configured to have a predetermined breaking strength, said breaking strength being at least sufficient to restrain a coupling when the connection between the restrained coupling and the tubular member is compromised.
 6. The device of claim 1 wherein said cord is configured to have a predetermined breaking strength, said breaking strength being at least sufficient to restrain a coupling that explosively releases from the tubular member.
 7. A device for a flotation apparatus having a first component joined to a second component at a connection, the device comprising: a stationary member; and a cord having a first and second end, said first end connected to the first component and said second end connected to said stationary member.
 8. The device of claim 7 wherein said cord is disposed within the flotation device.
 9. The device of claim 7 further comprising an engaging member provided on said cord first and second ends, said engaging members being selectively engagable with the first and second components.
 10. The device of claim 7 wherein said cord is configured to restrain the first component when the connection between the first component and said stationary member is compromised.
 11. The device of claim 7 wherein said cord is configured to have a predetermined breaking strength, said breaking strength being at least sufficient to restrain a first component that explosively releases from the second component.
 12. The device of claim 7 wherein said stationary member is a selected from a group consisting of a second coupling, tubular member, a head float, and a tail end.
 13. A flotation apparatus, comprising: a plurality of tubular members; couplings associated with said tubular members, said coupling interconnecting said tubular members; and a cord connecting at least two couplings.
 14. The device of claim 13 wherein said cord is disposed within at least one of said tubular members.
 15. The device of claim 13 further comprising an engaging member provided on said cord first and second ends, said engaging members being selectively engagable with the tubular member.
 16. The device of claim 13 wherein said cord is configured to restrain a coupling when the connection between the coupling and the tubular member is compromised.
 17. The device of claim 13 wherein said cord is configured to have a predetermined breaking strength, said breaking strength being at least sufficient to restrain a coupling that explosively releases from the tubular member.
 18. The device of claim 13 wherein said cord is configured to have a predetermined braking strength, said breaking strength being at least sufficient to restrain a coupling when the connection between the restrained coupling and the tubular member is compromised.
 19. A method for restraining components of a flotation system, comprising: tethering a first flotation system component to a second flotation component using a cord.
 20. The method of claim 19 wherein the first component is a coupling.
 21. The method of claim 19 further comprising disposing the cord within the flotation system.
 22. The method of claim 19 further comprising configuring the cord to be selectively engagable with the first component.
 23. The method of claim 19 further comprising configuring the cord to restrain the first component when the connection between the first component and the second component is compromised.
 24. The method of claim 19 further comprising configuring the cord to have a breaking strength that is at least sufficient to restrain a first component that explosively releases from the second component.
 25. The method of claim 19 wherein the first component is a first coupling and the second component is a second coupling. 